The present invention relates to a collector for conducting electrical current between the rotor and the stator in a homopolar machine; and more particularly to a high current metal fiber brush collector for such machines and a method of fabrication thereof.
Metal fiber brush collectors in homopolar motors and generators are known to be efficient, long-wearing, and capable of high current capacities. However, to achieve the high capacity in compact machines, the collector must contain a large number of brushes spaced closely together. For example, a compact 50 hp homopolar motor having a full-load current of 7460 amp. and a 5" diameter collector, requires approximately 300 closely mounted brushes. Present collector designs using spring-loaded solid brushes are incapable of such high density mounting. Due to the high thermal conductivity of the copper components in such designs, conventional techniques for soldering brushes, closely spaced to each other, in a ring geometry cause brush distortion or melting and electrical discontinuity of the soldered joints at adjacent brushes. Annealed metal fiber brushes, therefore, have been used the ring geometry and are mechanically seated with set screws. Consequently, thermal and electrical conductivity is reduced causing high contact resistance at their points of contact and excessively high operating temperatures.